Respiratory filter and sampling device

ABSTRACT

A combination respiratory filter and sampling device has been developed which collects airborne contaminants for respiratory exposure measurements. The devices, which fit existing commercial half-mask respirators, are generally smaller and lighter in weight than existing filters, and have low resistance to airflow, so they can be comfortably worn by people performing their normal work duties. Each device consists of at least a front, a middle and a back section which can be independently separated and analyzed by traditional laboratory techniques. The filtering and sampling media thicknesses and types can be adapted to target specific compounds.

This application is a division of application Ser. No. 08/324,072, filedOct. 14, 1994, now U.S. Pat. No. 5,651,810.

BACKGROUND OF THE INVENTION

The present invention is directed to a combined filter and sampler. Inparticular, the present invention is directed to a combined respiratoryfilter and sampling device which provides good filtering characteristicsand improved sampling capabilities in a single device.

Known air sampling methods for predicting human exposure include severaltechniques. Passive samplers are typically patches or disks which can bepinned to workers' clothing or affixed to structures. These samplersoperate by absorbing materials brought to them by air currents and bydiffusion through the air. No controls or measures of the airflow areavailable, so results will depend on where the sampler is placed and howit is used. Therefore, human exposure, and in particular respiratoryexposure, to particle-laden flows can be misleading because the particletrajectories for a passive sampler will differ from trajectories whereair is respired.

Active samplers typically consist of a fixed flowrate pump, filter, apre-filter if desired, and a power supply. The pump draws air throughthe filter at a prescribed, constant rate for a given period. Humanrespiratory exposures are estimated from the levels of contaminationthat remain trapped on the filter. If particle-laden flows are to beanalyzed, a cyclone device can be placed ahead of the filter. Thecyclone selectively prevents particles above a given size from enteringthe filter.

Generally, two types of active samplers are available: high volume andpersonal. Personal air samplers are typically designed to be portableand usually consist of a pump and a filter in combination. The pumpsdraw 0.5-2.0 liters per minute through tubular filters. The filters canbe pinned to a user's lapels, and the pump hung from a belt. High volumeair samplers draw much higher flowrates of air, but require large powersupplies and are typically fixed in position.

Existing active samplers, however, also have their own shortcomings.Active samplers are designed to estimate the average concentration ofcontaminants in the air, and not what a person in such an environmentwould have respired. Existing personal air samplers often draw an orderof magnitude less air than a human would and are not positioned at theface, where actual exposure would occur. Active samplers work well whencontaminants are vapors and exposure is constant and uniform, but duringepisodic or non-uniform exposure conditions, these samplers may notaccurately portray the levels of exposure during the workday.Additionally, high volume air samplers are not suitable for environmentswhere the worker is in motion over an extended area.

Several conventional mask filters are commercially available to trapcontaminants and prevent their respiration. Conventional mask filtersare, however, constructed with a single purpose in mind, to absorb asmuch material as possible in the most cost effective manner possible.These filters do not have the dual purpose of providing both an adequaterespiratory filtering mechanism and providing the filtering capabilityin a structure that optimizes the way materials are trapped by thefilter to enable accurate and efficient subsequent chemical analysis.Additionally, conventional mask filters are not designed for readydisassembly into component parts for chemical analysis.

Many existing mask filters are rather large or bulky due to theabsorption materials used and the way in which they are arranged. Thisleads to filters which are heavy and either cumbersome or uncomfortablefor a user particularly over long periods of time. As a result, a usermay choose to forego the protection that such mask filters providerather than tolerate these inconveniences.

It is apparent, therefore, that there exists a need for a combinationrespiratory filter and sampling device that provides filteringcapabilities at least equal to existing filters while at the same timeproviding sampling capabilities far superior to known sampling devices.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a combined filteringand sampling device.

It is a further object of the present invention to provide a combinedfiltering and sampling device having a plurality of filtering andcollection media layers in a stack, in which each layer may beindividually removed from the stack for analysis without disassembly ofthe entire stack.

Generally speaking, this invention fulfills the above-described andother objects of the invention by providing a sampling and filteringdevice comprising a first end member, a second end member in operativealignment with the first end member, first sampling and filtering meansinterposed intermediate the first and second end members and inoperative alignment therewith. First adjustable connecting means capableof engaging the first end member and the first sampling and filteringmeans and second adjustable connecting means capable of engaging thesecond end member and the first sampling and filtering means areprovided whereby adjustment of the first and second connecting means inopposing directions allows for removal of any one of the end members orthe sampling and filtering means without removal of any of the other ofthe end members or the sampling and filtering means.

In preferred embodiments of the present invention, the connectingmembers are screws.

In a preferred embodiment of the invention, the sampling and filteringmedia samples and filters Alachlor.

In another preferred embodiment the invention, the sampling andfiltering media samples and filters Glyphosate.

This invention further fulfills the above-described needs in the art byproviding a method of removing any layer from a multilayer combinedsampling and filtering device which device comprises first and secondend members, first and second sampling and filtering means intermediatethe first and second end members and first and second adjustableconnecting means engaging first and second end members and the first andsecond sampling and filtering means. The method comprises the steps ofadjusting the first connecting means in one direction therebydisengaging the first connecting means from the first sampling andfiltering means, adjusting the second connecting means in a directionopposite the direction of adjusting the first connecting means therebydisengaging the second connecting means from the first sampling andfiltering means and removing the first sampling and filtering means.

These and other features and advantages of the present invention will bedescribed in detail with reference to the following drawings, wherein:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a user wearing a filter mask thatutilizes the respiratory filter and sampling device of the presentinvention.

FIG. 2 is a vertical exploded cross sectional view of the componentparts of one embodiment of the respiratory filter and sampling device ofthe present invention taken substantially along line 2--2 of FIG. 1.

FIG. 3 is a cross sectional view of the respiratory filter and samplingdevice of one embodiment of the present invention taken substantiallyalong line 2--2 of FIG. 1.

FIG. 4 is an exploded perspective view of one embodiment of therespiratory filter and sampling device of the present invention.

FIG. 5 is a vertical exploded sectional view of a second embodiment ofthe respiratory filter and sampling device of the present invention.

FIG. 6 is a graph of flowrate versus pressure drop for an Alachlorfilter of the present invention.

FIG. 7 is a test setup for measuring pressure drop across the filter ofthe present invention.

FIG. 8 is a filter collection efficiency setup used to test filters ofthe present invention.

FIG. 8a is a plan view of the test port and nebulizer of FIG. 8.

FIG. 9 is a graph of particle size versus concentration for an Alachlorfilter of the present invention.

FIG. 10 is a graph of particle size versus collection efficiency for anAlachlor filter of the present invention.

FIG. 11 is a test setup for comparing filters of the present inventionwith prior art impingers.

FIG. 12 is a comparison of mass concentrations collected by filters ofthe present invention and by prior art impingers.

FIG. 13 is a table of pressure drop measurements of a Glyphosate filterof the present invention.

FIG. 14 is a graph of particle size versus collection efficiency for aGlyphosate filter of the present invention.

FIG. 15 is a cross sectional view of the respiratory filter and samplingdevice of FIG. 3 employing an alternative set of connecting members.

FIG. 15a is a cross-sectional view of the respiratory filter andsampling device of FIG. 15 employing another alternative set ofconnecting members.

FIG. 16 is a cross-sectional view of a four layer sampling and filteringdevice of the present invention utilizing long and short connectingmembers.

DETAILED DESCRIPTION OF THE INVENTION

A respiratory filtering device is a device designed to condition airprior to inhalation. In particular, a respiratory filtering devicegenerally includes one or more layers of a medium which may have a poresize smaller than the average size of an undesirable particulate fortrapping the particulate matter and to thereby prevent respirationthereof. Alternatively, the medium may have a chemical impregnatedtherein which can effectively absorb or neutralize an undesirablecontaminant. Typical respiratory filters are effective for a limitedexposure time after which they are disposed of as a unit. Samplingdevices, on the other hand, trap contaminants for analysis in situ or ata later time. Therefore, portable sampling devices must be amenable toat least partial disassembly or interfacing with a chemical analyzer,such as, for example, a mass spectrometer.

A combined filtering and sampling device must, therefore, provide thefunctions of both conditioning the air to be respired and be capable ofdisassembly for analysis. Furthermore, for such a device to becommercially acceptable, it should be lightweight, should not exhibitexcessive pressure drop, and should be readily adaptable withconventional face masks.

Referring to FIG. 1, respiratory filter and sampling device 10 accordingto the present invention is illustrated mounted in a conventional filtermask 12. Device 10 is capable of being utilized in conjunction with mostcommercially available mask filters including half-masks and full facemasks. A preferred mask for use with the filtering and sampling deviceof the present invention is the Survivair Blue 1 manufactured byLomasec, Inc. The masks capable of being utilized in conjunction withdevice 10 have a valve such as that generally referred to as 14 in FIG.1 which controls the flow of air through devices 10. During inhalation,the valve is closed so that all air that is ultimately going to berespired by the user is routed through devices 10. During exhalation,valve 14 opens to allow exhaled air to bypass devices 10. The samplingand filtering media of devices 10 can be removed for analysis andmeasurement to determine exposure levels as will be described below.When the Survivair Blue 1 face mask is utilized, two sampling andfiltering devices 10 are placed on the mask. Total exposure levels arethen determined by combining the analysis data from the two devices. Theresistance to airflow of a mask, such as mask 12, with two devices 10attached thereto, will be one half that of a mask with one device 10,allowing the wearer to breathe more easily because the resultingpressure drop is not as great.

FIGS. 2-4 illustrate a typical assembly of one embodiment of a combinedsampling and filtering device 10 according to the present invention. Asbest shown in FIG. 2, the combined sampling and filtering device 10 is amultilayered device. The number, type, size and composition of theconstituent layers of the device 10 vary according to the airborneparticulates, droplets, or vapors for which one desires to test orfilter. All of the embodiments of the present invention, however, sharecertain common structural characteristics, as will be discussed below indetail.

It therefore should be appreciated that many different layeringcombinations and constituents can be used without departing from thespirit and scope of the present invention. Combinations of particularlayers found useful in filtering and testing for particular materialswill be discussed below. It should further be understood that theinformation on the materials that can be filtered or isolated forfurther analysis is for exemplary purposes only and is by no means meantin any way to be construed as limiting the materials that can befiltered or isolated by the present invention or the types orcombinations of materials that can be used to isolate or filterparticular elements.

The structure of device 10 is adaptable to receive a wide range offiltering and sampling media. Commercially available filtering andsampling media such as fiberglass or HEPA pads may be placed within orbetween the spacers. In addition, particulate-type sampling andfiltering media such as activated carbon, molecular sieve material orsilica gel may be placed within the spacers and held in place by wiremesh screens in a layer having a uniform thickness. Depending upon thetype of contaminant sought to be tested for or filtered out, the wirescreens may also act as a collection media, as by the process ofadsorption. Chemicals collected by the screens may be detected byanalysis and combined with the data obtained from analysis of thesampling and filtering media to determine total exposure levels. Bychoosing an appropriate number and combination of filtering and samplingmedia, device 10 can be utilized to sample and filter a wide range ofairborne chemical and particulate contaminants.

A combined sampling and filtering device 10, as shown in FIGS. 2-4, is amultilayer stack 16. Stack 16 comprises first end member 18 includingmask adapter 20, second end member 22, and alternating layers of wiremesh screens 26, 28, 30, and 32, spacers 24, 34 and 36, and samplingand/or filtering media 38, 40, and 42 placed between end members 18 and22. End members 18 and 22 and spacers 24, 34 and 36 may be annular.Stack 16 is held together by adjustable connecting members 44 and 46which intersect selected layers of stack 16. Connecting members 44 and46 may be, for example, screws. In one embodiment of the presentinvention, connecting members 44 and 46 extend oppositely from endmembers 22 and 18, respectively, toward spacer 24 thereby defining toplayer 19 and bottom layer 17. As shown in FIGS. 2-4, connecting members44 and 46 are screws, and are in threaded engagement with threaded holes56. Connecting members 44 and 46 allow removal of individual layers ofstack 16 without disassembly of the entire stack 16. In one preferredembodiment, as best shown in FIG. 15, connecting members 300 and 302extend between end member 18 and end member 22 whereby each ofconnecting members 300 and 302 intersect each layer of stack 16.

First end member 18, second end member 22, and spacers 24, 34 and 36 arepreferably manufactured of nylon. Wire mesh screens 26, 28, 30 and 32are preferably made of stainless steel having a mesh size in the rangeof about 60 mesh. The stainless steel wire preferably has a diameter ofabout 0.0075 inches. Connecting members 44 and 46 can be made ofstainless steel but are preferably made of nylon, or a similarlightweight durable material, to keep the weight of device 10 to aminimum.

As best shown in FIG. 4, end members 18 and 22, and spacers 24, 34 and36 are annular members having a number of holes equally spaced about theouter periphery thereof. Holes 48, 50, 52, 54 and 56 in members 18, 22,34, 36 and 24, respectively, may be through holes or threaded holes or acombination of both depending upon the size and type of connectingmembers 44 and 46. Screens 26, 28, 30 and 32 include slots or holes 58,60, 62 and 64, respectively, located about the outer periphery thereofto accommodate connecting members 44 and 46 therethrough. Similarly,medium 38 may include slots or holes 66 also located about the outerperiphery thereof. Alternatively, medium 38 may have a diameter smallerthan spacers 24, 34 and 36 and occupy the entire inner diameter of asingle spacer. Screens 26, 28, 30 and 32, end members 18 and 22, andspacers 24, 34 and 36 are of substantially the same outer dimension sothat screens 26, 28, 30 and 32 are held taut between members 18 and 22and spacers 24, 34 and 36. In addition, screens 26, 28, 30 and 32overlay spacers 24, 34 and 36 and end members 18 and 22 so as toseparate spacers 24, 34 and 36, end members 18 and 22, and sampling andfiltering media 38, 40 and 42. Maintaining screens 26, 28, 30 and 32taut also ensures media 38, 40 and 42 are contained within defined areasand in uniformly packed layers.

As described, sampling and filtering device 10 consists of a pluralityof distinct layers. Successive layers are built up by interposingbetween first end member 18 and second end member 22, as required, anynumber of layers of screens, spacers and sampling and filtering media,one on top of the other and in operative alignment with each other. Thelayers are then secured, as described, utilizing connecting members suchas connecting members 44 and 46, which may be screws. In accordance withthis invention, connecting members, such as connecting members 44, areadjustably removable by sliding in one direction while connectingmembers such as connecting members 46 are adjustably removable bysliding in a second direction opposite to the direction of sliding ofconnecting members 44.

With reference to device 10 as shown in FIGS. 2-4, a typicalconstruction sequence for bottom layer 17 is as follows. To begin with,screen 32 is placed on first end member 18 in operative alignmenttherewith and with holes or slots 64 aligned with holes 48. Spacer 36 isthen placed on screen 32 in operative alignment therewith and with holes54 aligned with holes 64 thereby creating receptacle 68 for samplingand/or filtering media. Sampling and/or filtering media 42 is nextplaced in receptacle 68. Screen 30 is then placed on spacer 36 inoperative alignment therewith and with holes 62 aligned with holes 54thereby forming a cover for receptacle 68 and for maintaining a uniformlayer of media 42. Additionally, spacer 24 is placed on screen 30 inoperative alignment therewith and with holes 56 in alignment with holes62. Connecting members 46 are then inserted into every other hole ofholes 48 and then engaged with the correspondingly aligned holes ofholes 64, 54, 62 and 56. In the embodiment of the present invention,shown in FIGS. 2-4, connecting members 46 are screws and holes 56 arethreaded, and connecting members 46 are tightened into threadedengagement with holes 56.

A typical construction sequence for top layer 19 on top of bottom layer17 is as follows. HEPA pad 38, or other sampling and/or filtering media,is placed on top of spacer 24 in operative alignment therewith and withholes 66 aligned with holes 56. Screen 28 is then positioned on pad 38in operative alignment therewith and with holes 60 aligned with holes66. Spacer 34 is then located on screen 28 in operative alignmenttherewith and with holes 52 aligned with holes 60 thereby creatingreceptacle 70. Sampling and/or filtering media 40 is then placed inreceptacle 70. Screen 26 is then positioned on spacer 34 in operativealignment therewith and with holes 58 aligned with holes 52 therebyforming a cover for receptacle 70. Second end member 22 is then placedon screen 26 in operative alignment therewith and with holes 50 alignedwith holes 58. Connecting members 44 are then inserted through everyother hole of holes 50 and then engaged with the correspondingly alignedholes of holes 58, 52, 60, 66 and 56 in a direction opposite to that ofconnecting members 46. Connecting members 44, which are screws, are thentightened into engagement with threaded holes 56.

In addition to the above possible construction sequences for device 10,connecting members 44 and 46 may be used as alignment tools as eachlayer is placed on top of the other. Furthermore, while placing samplingand/or filtering media into receptacles 68 and 70, such as a particulatetype sampling and/or filtering media, it may be advantageous to utilizeclamps to keep spacers 34 and 36 compressed against the adjacent screenand to thereby prevent the particulate from getting between the spacerand the screen.

In the embodiment shown in FIGS. 2-4, and as just described, connectingmembers 44 and 46 are removable in opposing directions. Connectingmembers 44 are removable only through end member 22 while connectingmembers 46 are removable only through end member 18. Stack 16 is asingle integrated sampling and filtering device because both sets ofconnecting members 44 and 46 are in threaded engagement with spacer 24.The opposing relation of connecting members 44 and 46 permits the layersof sampling and/or filtering media 38, 40 and 42 to be independentlyseparated from device 10 for analysis by standard laboratory techniques.It is to be noted that connecting members 44 and 46 engage alternatingholes of holes 56.

To remove any single layer from stack 16, connecting members 44 or 46are disengaged from threaded holes 56 and slidably adjusted to free thedesired layer. For instance, to remove medium 38, loosen connectingmembers 44 to disengage them from threaded holes 56. Adjust connectingmembers 44 by sliding and lifting second end member 22, screen 26,spacer 34 and screen 28, as a unit, off spacer 24 and remove samplingand/or filtering medium 38. To remove sampling and/or filtering medium42, turn device 10 so that first end member 18 is facing up to preventmedia 48 from falling out. Loosen connecting members 46 to disengagethem from threaded holes 56. Slidably adjust connecting members 46 toallow screen 30, spacer 36 and screen 32 to be removed as a unit. Asdescribed, any individual layer of stack 16 may be removed withoutdisturbing every other layer.

To prevent air leakage from between the spacers, a sealing element suchas, for example, plastic adhesive tape, not shown in the drawings, iswrapped around the periphery of the assembled device 10. Alternatively,a compound which would provide an airtight seal, yet still allowdisassembly of device 10, such as a silicon gel, could be placed betweenthe spacers.

In a preferred embodiment of the present invention, as shown in FIG. 15,device 10 is altered by utilizing connecting members 300 and 302.Connecting members 300 and 302 intersect each layer of stack 16providing great flexibility in removing any single layer of stack 16.Connecting members 300 and 302 may be smooth rods or threaded rods.Retaining members 304 and 306 may be elements, such as clips or threadednuts, which attach to the ends of connecting members 300 and 302respectively, and apply compressive loads to stack 16. The compressiveloads serve to hold the individual elements in stack 16 togethertightly. Alternatively, connecting members 300 and 302 may beconventional screws with heads 308 and 310 respectively in which casemembers 300 and 302 are inserted in alternating holes and extend ineither the same direction, or in opposite directions as illustrated inFIG. 15a.

In the embodiment illustrated in FIG. 15 where connecting members 300and 302 are rod-like members without a head, retaining members 304 and306 can be removed from alternate connecting members 300 and 302, toenable sliding adjustment of connecting members 300 and 302 in opposingdirections. This is accomplished by initially removing a first retainingmember 304 from a first connecting member 300. A second retaining member306 is then removed from a second connecting member 302 adjacent firstconnecting member 300. One then proceeds in this alternating manneruntil all connecting members 300 are free to slidably adjust in onedirection and all connecting members 302 are free to slidably adjust inthe direction opposite that of connecting members 300.

With further reference to FIG. 15, layer 34 may be removed bydisengaging connecting members 300 and 302 from selected layers of stack16 by slidably disengaging connecting members 300 and 302 in oppositedirections, as follows. Retaining members 304 are first removed fromconnecting members 300. Connecting members 300 are then disengaged fromeach layer of stack 16 except layer 22. Retaining members 306 are thenremoved from connecting members 302. Connecting members 302 aredisengaged from member 22, screen 26, spacer 34 and screen 28. Spacer34, along with screens 26 and 28, are now free from connecting members300 and 302 to be removed.

To remove medium 38, disengage connecting members 300 from end member18, screen 32, spacer 36, screen 30, spacer 24 and medium 38. Connectingmembers 300 remain engaged with screen 28, spacer 34, screen 26 and endmember 22. Disengage connecting members 302 from end member 22, screen26, spacer 34, screen 28 and medium 38. Connecting members 302 remainengaged with spacer 24, screen 30, spacer 36, screen 32 and end member18. Medium 38 is free from connecting members 300 and 302 and may beremoved from stack 16.

Referring now to FIG. 15a, a preferred form of the present invention isshown including connecting members 300 and 302 which may be conventionalscrews having heads 308 and 31 respectively. As in the otherembodiments, holes 48, 50, 52, 54 and 56 may be through holes orthreaded holes, or a combination of both. Retaining members 304 and 306may be utilized at one end only of connecting members 300 and 302 asrequired to compress the members of device 10. Removal of any one ormore layers from device 10, as shown in FIG. 15a, would be accomplishedmuch the same as for removal of any one or more layers from device 10 asshown in FIG. 15. Of course, however, connecting members 300 arerestricted to removal, by sliding, in only one direction. Similarly,connecting members 302 are restricted to removal in only one direction,by sliding, in the same or opposite direction from connecting members300 depending upon installation.

A second embodiment of a combined sampling and filtering deviceaccording to the present invention is shown generally as 100 in FIG. 5.Device 100 is generally similar to device 10 and comprises first endmember 136 including mask adapter 138, second end member 114 and spacer126. Interposed between second end member 114 and spacer 126 are screens116, 118, 122 and 124, fiberglass pads 102, 104, 106 and 108 and spacer120. Interposed between first end member 136 and spacer 126 are screens128, 130 and 134, fiberglass pad 110, mist pad 112 and spacer 132. Endmembers 114 and 136 and spacers 120, 126 and 132 may be annular andinclude several through holes or threaded holes equally spaced about theperiphery thereof as in device 10. Device 100 is held together byconnecting members 140 and 142 in similar fashion to connecting members44 and 46 or 300 and 302 of device 10. Assembly and disassembly ofdevice 100 is carried out in a manner similar to that for device 10. Theend members, spacers and screens of device 100 are made of the same typeof materials as device 10.

It is to be noted that any combination of screens, spacers and samplingand filtering media may be interposed between the main structuralcomponents hereinbefore generally referred to as a first end member,second end member and spacers. Thereby, a combined sampling andfiltering device may be provided for sampling and filtering many knowntypes of pesticides, toxins or other airborne contaminants simply bybuilding up the required type and number of sampling and filteringmedia.

In addition, while the two embodiments of the combined sampling andfiltering device of the present invention described herein contain threespacers between the first and second end members, any number of spacers,i.e. two, four, five, six, etc., could be employed. This would provideareas for insertion of additional types and layers of sampling andfiltering media. Furthermore, and regardless of the number of spacers orlayers of sampling and filtering media employed, connecting members,such as connecting members 44 and 46, 140 and 142 or 300 and 302, may beof varying lengths. For example, a four layer stack, as best illustratedin FIG. 16, may include end members A and D and sampling and filteringmedia layers B and C intermediate end members A and D. Alternateconnecting members of connecting members E may extend through layers A,B and C while the other connecting members of connecting members Eextend through only layers A and B. Connecting members F would extendthrough layers D and C. In such a configuration, therefore, it ispossible to disengage the longer connecting members of connectingmembers E and connecting members F from layer C and remove layer Cwithout disengaging the shorter connecting members of connecting membersE. Therefore, the engagement between layers A and B need not beloosened. As those skilled in the art will recognize, the generalconcept of providing some connecting members which are shorter or longerthan others can be carried out in a variety of ways. This concept can beused in conjunction with a filter having a large number of filteringlayers by simply increasing the number of connecting members usedtherewith.

As illustrated in FIGS. 2-4 and FIG. 5, mask adapters 20 and 138,respectively, include flanges 146 and 148 respectively. Flanges 146 and148 are designed to be engaged with the filter ports of a conventionalfilter mask 12 such as the Survivair Blue 1. Alternatively, flanges 146and 148 may be replaced by a threaded mask adapter for engagement withthe filter ports of other conventional filter masks such as a ScottModel 65 Twin Cartridge Respirator.

EXAMPLE 1

In one embodiment of the present invention, the particular combinationof layers of filtering media has been found to be particularly effectivein filtering Alachlor, the active ingredient in the commercial pesticideLasso®. This embodiment, illustrated in FIGS. 2-4, includes two silicagel layers 40 and 42 and a particulate collection pad 38. Each layer ofsilica gel and the particulate collection pad filters and collects, forlater analysis, Alachlor in vapor or liquid phase, or attached toparticles. Receptacle 70 holds a layer 40 of chemically pure silica gel(SKC Brand, 20/40 available from SKC, Inc.) Silica gel layer 40 is 1/4inch thick and is the primary collection medium. Screens 26 and 28maintain silica gel layer 40 in receptacle 70 in a uniform layer.Receptacle 68 holds a layer 42 of the same type of pure silica gel in a1/8 inch thickness. Screens 30 and 32 maintain silica gel layer 42 in auniform layer within receptacle 68. Layer 42 collects any breakthroughfor quantification. Interposed between screen 28 and spacer 24 is a highefficiency collection pad 38, such as a TC-21C-488 available from the 3MCompany or similar pad. Pad 38 is used to trap particulate matter. Wirescreens 26, 28, 30 and 32 are held taut to ensure that thin, uniformlayers of filtering media will result.

Air respired through combined sampling and filtering device 10 is drawnthrough screen 26 and into and through silica layer 40, the primarycollection media, where substantially all of the Alachlor respired istrapped. Air is then drawn through screen 28 and into and through highefficiency collection pad 38 where substantially all particulate matteris trapped. Air is then drawn through screen 30 and into and throughsilica layer 42 where Alachlor not collected by silica layer 40 iscollected to quantify breakthrough.

Testing was performed on device 10 to determine pressure drop across thefilter and filtering efficiencies. The pressure drop, reported in FIG. 6and discussed further below, shows that the device 10 offers lowresistance to airflow so that wearers can breathe through the filterswithout significantly affecting respiration. Filtering efficiencies, asreported in FIGS. 9 and 10 and discussed below, show good resultscompared to other types of filters.

Typically, normal resting respiration is approximately 6 liters perminute (lpm) while respiration rates during mild exercise range fromabout 10 lpm to about 15 lpm. As can be seen in FIG. 6, the pressuredrop through a single device 10 at 10 lpm is about 1/2 inch of watercolumn pressure. This is a low resistance to airflow, thereby allowingwearers to breathe through device 10 without significant adverse affectsto their respiration. Lower resistance to airflow, of about 1/4 inch ofwater column pressure, will actually be experienced because two devices10 are typically utilized with conventional masks such as mask 12. Humanfactors studies conducted by the applicants indicate that the pressuredrop measured across device 10 is comparable with commercially availableconventional filters. The pressure drop testing setup is illustrated inFIG. 7 and includes vacuum pump 150, throttle valve 152, flow meter 154and pressure gauge 156 connected in series. Control values of pressuredrop versus flowrate through the system, without device 10 in place,were measured over a range of up to 41 liters per minute. Device 10 wasthen attached upstream of the pressure gauge and the pressure dropversus flowrate through the system measured again. The pressure dropthrough device 10 was then calculated by subtracting the controlpressure drops from the test pressure drops at each given flowrate. Thecorrected data showing about 1/2 inch of water pressure drop at 10 lpmacross a single device 10 is reported in FIG. 6.

The efficiency of device 10 to capture particulate matter was determinedby nebulizing liquids and measuring the droplet concentrations drawninto a tube without and with device 10 in place. FIG. 8 best illustratesthe setup and interconnection of components utilized for this test. Anebulizer 202 having a reservoir 204 filled with a test liquid, such ascorn oil or Roundup, is connected through a flow meter 206 to acompressed air line 208. When regulator 210 is opened, the test liquidis dispersed in droplets in front of test port 212, as best shown inFIG. 8a. A sampling and filtering device 10 may be attached to port 212to test the device, or port 212 may be open to collect control values.Connected to port 212 are a vacuum pump 214, flow meter 216 and anaerodynamic particle sizer 218.

As reported in FIG. 9, at least a tenfold decrease in particleconcentration was observed over the respirable range of diameters (about0.5 to 10.0 microns) when device 10 is compared with the same systemwithout a filter. The data reported in FIG. 9 is also reported in FIG.10 as collection efficiency versus particle diameter. FIG. 10illustrates that 90% to 100% of particles in the respirable range ofdiameters are collected by device 10. In particular, in two separatestudies represented by Series 1 and Series 2, sampling and filteringdevice 10 trapped about 90% of particles between about 0.5 to 2.0microns and about 100% of particles between about 2.1 to 10.0 microns.These data show that the silica gel layer is an effective particletrapping matrix.

In addition, device 10 was tested as a sampler and the results werecompared with an impinger type personal sampler. The test setup for thisexperiment is shown in FIG. 11 and includes a chamber 250, spray nozzle252, pump 254 and reservoir 256. In this test, a 2.5% solution of Lasso®was sprayed using an SS8001 nozzle from Spraying Systems, Inc., Wheaton,Ill. The 2.5% solution of Lasso® is a commonly used spray concentrationin the field. The Lasso® was mixed with air drawn through screen 258,and drawn into two devices 10 by vacuum pumps 260 at 12 lpm each.Simultaneously, the Lasso® solution was drawn through the impingers 262by vacuum pump 264 at 1 lpm each.

Devices 10 and the impingers were then chemically analyzed for thequantity of Alachlor, the active ingredient in Lasso®. The results fortwo separate studies represented by Series 1 and Series 2, reported inFIG. 12, show very favorable comparison of devices 10 as samplers withthe impingers. The studies show that Alachlor is recovered from thesilica when methanol is used as a solvent.

EXAMPLE 2

In another embodiment of the present invention, the filtering media aredesigned to collect Glyphosate. As best shown in FIG. 5, device 100includes several fiberglass pads 102, 104, 106, 108, and 110 which arethe primary filtering and collection media. A mist pad 112 is alsoprovided to filter out wet vapor. As shown in FIG. 5, the device 100includes first end member 136, second end member 114, spacers 120, 126and 132 and screens 116, 118, 122, 124, 128, 130, and 134. Members 114and 136 and spacers 120, 126 and 132 may be annular members providedwith several through holes or threaded holes equally spaced about theperiphery thereof. Second end member 14 and spacers 120 and 132 are 1/8inch thick, while spacer 126 is 1/4 inch thick. First end member 136includes mask adapter 138.

Device 100 is held together in a fashion similar to device 10 describedabove. Connecting members 140 and 142 extend from spacer 114 and fromspacer 136 to allow disassembly and removal of individual layers ofdevice 100 without disassembly of the whole device 100.

Pressure drop and filtering efficiency tests were also conducted on theGlyphosate devices 100. The pressure drop data reported in FIG. 13 showsa pressure drop across a single sampling and filtering device 100 ofapproximately 0.30 inches of water column pressure at 10 lpm of airflow. This is a very low pressure drop and allows the wearer to breathethrough device 100 without significant adverse affects to respiration,even during mild exercise. Collection efficiency data for the device 100is reported in FIG. 14 and shows about 90% to 100% collection forparticle diameters in the respirable range of diameters.

As shown by the test results for the two examples above, the combinedsampling and filtering devices of the present invention provide goodfiltering characteristics as well as good sampling characteristics. Inaddition, because the combined sampling and filtering devices measureactual human respiratory exposure, thereby requiring no data reduction,analysis of human exposure rates from the devices is more accurate. Thecombined sampling and filtering devices of the present invention alsoprovide structural flexibility allowing selective removal of any singlelayer of sampling and/or filtering media for laboratory analysis withoutrequiring complete disassembly of the device.

While this invention has been described as having a preferred design, itis understood that it is capable of further modifications, uses and/oradaptations, following the general principle of the invention andincluding such departures from the present disclosure as come withinknown or customary practice in the art to which the invention pertains,and as may be applied to the central features set forth above, and fallwithin the scope of the invention of the limits of the appended claims.

I claim:
 1. A device for sampling and filtering a herbicide comprising:afirst end member; a second end member in operative alignment with saidfirst end member; a plurality of fiberglass pads arranged in a stack andthrough which air is first respired for trapping the herbicide, saidplurality of fiberglass pads being intermediate said first and secondend members and in operative alignment therewith; a mist pad inoperative alignment with said plurality of fiberglass pads and throughwhich air is respired after being respired through said plurality offiberglass pads for preventing respiration of wet vapor, said mist padbeing intermediate said first and second end members; first adjustableconnecting means for engaging at least said first end member; and secondadjustable connecting means for engaging at least said second endmember; said first and second connecting means engaging said pluralityof fiberglass pads and said mist pad for maintaining same in tightengagement with said first and second end members.
 2. The device ofclaim 1 including five fiberglass pads.
 3. The device of claim 1 whereinthe herbicide includes the chemical glyphosate.
 4. The device of claim1, wherein each of said first and second end members, said plurality offiberglass pads, and said mist pad include holes located about theperiphery thereof for slidably engaging said first and second connectingmeans therewith.
 5. The device of claim 1, wherein said first and secondconnecting means are rods.
 6. The device of claim 5, furtherincluding:first retaining means for maintaining said first connectingmeans in engagement with said first end member, said plurality offiberglass pads, and said mist pad; and second retaining means formaintaining said second connecting means in engagement with said secondend member, said plurality of fiberglass pads, and said mist pad.
 7. Thedevice of claim 6, wherein said first and second connecting means arethreaded.
 8. The device of claim 7, wherein said threaded connectingmembers are screws.
 9. The device of claim 1, wherein said second endmember includes a filter mask adapter.
 10. The device of claim 9,further comprising a mask adapted to be placed over at least the noseand mouth of a wearer, the mask having at least one aperture thereinadapted to receive and engage the filter mask adapter.
 11. The mask ofclaim 10, wherein air inhaled by a wearer passes through said samplingand filtering device at a flow rate measured in liters per minute, theresistance to airflow of said sampling and filtering device isquantified as a pressure drop measured in inches of water columnpressure, and said pressure drop is less than about 0.0558 times saidflow rate.
 12. The device of claim 1, wherein said first and secondconnecting means are adjustable to allow disassembly and removal ofindividual fiberglass pads without disassembly of the entire samplingand filtering device.
 13. A device for sampling and filtering aherbicide comprising:a first end member; a second end member inoperative alignment with said first end member, wherein said second endmember includes a filter mask adapter; a plurality of fiberglass padsarranged in a stack and through which air is first respired for trappingthe herbicide, said plurality of fiberglass pads being intermediate saidfirst and second end members and in operative alignment therewith; amist pad in operative alignment with said plurality of fiberglass padsand through which air is respired after being respired through saidplurality of fiberglass pads for preventing respiration of wet vapor,said mist pad being intermediate said first and second end members;first adjustable connecting means for engaging at least said first endmember; and second adjustable connecting means for engaging at leastsaid second end member; said first and second connecting means engagingsaid plurality of fiberglass pads and said mist pad for maintaining samein tight engagement with said first and second end members; wherein eachof said first and second end members, said plurality of fiberglass pads,and said mist pad include holes located about the periphery thereof forslidably engaging said first and second connecting means therewith; andwherein said first and second connecting means are adjustable to allowdisassembly and removal of individual fiberglass pads withoutdisassembly of the entire sampling and filtering device.